Preheat the oven to 180ºC, fan 160ºC, gas 4. Prick the potatoes with a fork to prevent them splitting in the oven and bake for 45 minutes.
Just before the potatoes are due to be ready, heat the oil in a small frying pan and cook the bacon for 5 minutes. Add the chicken and toss with the bacon for 1 minute to warm through. Stir through the spinach and half the grated cheddar.
Remove the potatoes from the oven, make a cross in each and ease open. Fill with the cheesy bacon and chicken mixture and top with the remaining cheddar. Heat under a hot grill until the cheese is melted and bubbling. Season with a little freshly ground black pepper and serve.